Casting a windmill gear in grey iron

New meaning to the word "castaway"...

 

A #7 gear cutter, in 5DP & 14.5 PA ... should cut the foam like butter.

 

We know Dave can do this in lost plastic, but with the proper tooth profile it really lends itself to lost foam. THINKING!

 

This pattern (with no draft) really lends itself to the lost PLA method (in my opinion).
And if Dave can hold the surface finish quality that was on the sample parts he sent me, then I would say lost PLA is a shoe-in for this application.

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Want me to route you a foam pattern, Kelly?

 

Accurate restoration would require a green sand casting, would it not?

 

I think accurate restoration would mean machining a new gear from a cast iron blank, and I am sure that is how they made the original gears.
I know they did cast the teeth on gears in the old days, at least on large gears, because I have seen the patterns at Soule.
But I have never seen a small gear pattern with teeth on it.
Below are patterns at the Soule foundry/museum.






























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Pretty patterns. I've seen lots of all cast gears on old farm equipment, not sure I've seen any this deep however. Ed may know whether they were originally cast teeth.

 

If you make it I'll pour it, but I thought you had started some lost foam Andy?
My interest here is see how mold ready a pattern is from a 3D printer. Even though I enjoy making patterns the old school way, developing a method to go directly into the sand with minimal finishing work intrigues me.
If I had to make a foam pattern, I might as well make a wooden one and use it on the next windmill.
But, if a thin plate pattern was printed 3D with a double shrink, cast in aluminum and then had the foam glued to it, the hot wire could make short work of the tooth form. Attach the hub and sprue, coat and pour.

I doubt that Pat. What you can be sure of is they were not loose patterns. They were probably a match plate so they could be done in multiples. There may have been only one master, so it is long gone, and the matchplate done in white metal for durability. Just guessing here, but I don't think they were doing that kind of machining in that era.

 

Only for Concours windmills.

 

I do lost foam where it fits for me. I'm stubbornly pursuing green sand here.

With a little work I can take the undrafted file and mill it out of foam in a 3D router.

PM me your address and I'll end you a printed pattern. They are close but still take a fair amount of finishing and the plastic does not sand well, in my experience. I have to fill then sand to prepare a pattern. And I've been struggling at doing that on this gear.

I will print a thin plate 3D print if you like. Tell me the total shrink you want to add for aluminum then iron.

 

Not to spoil everyones fun but when you get this cut a cast blank and be done!

 

Why not just buy custom gears?

 

OK, if you do that I will pour it. If you add the boss I will bore the core and add the riser. I'll PM my address.
Ed was going to print a zero draft pattern for me to try when he gets back from the meet. In this case since he is the end user I want to see if I can work with the patterns he generates. I suggested 1%, but left it to him for the allowance.
Has anyone had two patterns together and verified they mesh decently or checked center distance for whatever shrink was added?

 

I am pretty sure they were doing that sort of machining in that era, but exactly what era is important.
Many technical advances happened sort of around 1840, and seemed to accelerate after the Civil War.
The old steam engines after the Civil War were very advanced, as were many machining techniques. The best machine tools in the 1860's were from England and perhaps other parts of Europe.

Here is a post from Athanor on the "The Steampunk Forum":
I have not verified any of this, so don't quote me on it.

Small gears, for mass-produced clocks and watches, would usually be die-stamped from brass strip; better quality ones would be machine finished. Larger gears might be machined from brass, bronze, cast iron or steel blanks, either directly using a tooth-shaped milling cutter (or more correctly, a cutter shaped like the gap between two teeth), or generated using a special cylindrical cutter known as a hob; or cast directly in sand moulds, from cast iron, brass or bronze, and machined or ground to a finish.

Bigger gears, such as might be used in large steam engines or for heavy machinery, might have individual teeth cast, usually from iron, then keyed, bolted or riveted to the wheel centre; others used drop-forged teeth, again fitted individually into the wheel centre. The older the machine, the more likely it would be to have individually cast or forged gear teeth.

Older machinery, such as wind or water mills, might have teeth cut from a hard wood, such as lignum vitae or ironwood, mounted onto a wheel centre which might be cast iron, forged iron or wood. Lignum vitae was used because it contains natural oils and is to some extent self-lubricating; cast iron, which contains graphite, also has this advantage. This inserted-tooth method of gear construction goes back to at least Roman times.

Profile grinding of gear teeth is a more modern approach, but was certainly in use in the early 20th century. A cast, drop-forged or flame-cut blank is used, and the tooth profile finished by grinding.

Gear manufacturing is a rather specialised subject and the above is an outline only; but any process one can imagine has probably been used to make gears somewhere, at some time!


« Last Edit: July 07, 2010, 01:22:23 am by Athanor »


From this web page:
https://ugears.online/blogs/news/history-of-gears

However, in the 19th century, form cutters and rotating cutters were first used and it was then in 1835 when the English inventor Whitworth patented the first gear hobbing process.

 

I like this quote.

Concours you know, and that involute cutter is only for 14 to 16 tooth and a bargain at about $400 out of Hartford and that isn't counting the dividing head. but you are correct that it is one way to do this.

 

Forgot about the foundry on my home turf. The owner made from mostly scratch a 150 HP Case steam engine. Its has several cast gears but I don't know about the draft or process. Definitely wasn't foamed but they did have some printed sand molds made for other parts.